Fuel additives

ABSTRACT

There is described a fuel additive composition comprising an oleic alkanolamide and an alkoxylated oleic acid. There is also described a fuel composition comprising a hydrocarbon fuel and a fuel additive comprising an oleic alkanolamide and an alkoxylated oleic acid and also a method of running a combustion engine using the fuel if the invention.

Surfactants have long had utility as additives which can affect theperformance of fuels such as gasoline and diesel. British Patent No2217229 describes a solubilising compound as a fuel additive. Inparticular there is described a composition comprising;

-   -   48 parts by volume of an alcohol ethoxylate;.    -   3–8 parts by volume of lauric diethanolamide;    -   3–8 parts by volume of oleic diethanolamide; and    -   1.5–4 parts by volume of a polyglycol ether such as ethoxylated        oleic acid.

Such compositions are useful as fuel additives and enable thesolubilisation of water in fuels thus reducing its potential corrosiveeffect. However, the compositions are disadvantageous in that, interalia, they require a high additive to fuel ratio. Furthermore, they donot address the problems of emissions of gases such as CO, CO₂ and NOx.

International Patent Application No WO 98/17745 describes an alternativeformulation which comprises,

-   -   25% w/w of a diethanolamide,    -   50% w/w of an ethoxylated alcohol, and    -   25% w/w of a fourteen carbon chain fatty acid with seven        ethoxylate groups.

WO '745 especially describes fuel compositions comprising, inter alia,an additive made up of a fatty acid diethanolamide, an alcoholethoxylate and an ethoxylate of a fatty acid, the degree of ethoxylationbeing selected so that a long term stable fuel composition is formedand, in particular, wherein, by carefully selecting the degree ofethoxylation, a balanced blend can be produced.

Whilst such additives provide significant reductions in emissions andare useable at low concentrations, there is still a need for a fuelcomposition which is capable of reducing emissions whilst maintainingperformance levels and which may be even more cost effective to use.

We have now surprisingly found that a more advantageous additive can beprepared without the use of an ethoxylated alcohol

Thus according to the invention we provide a fuel additive compositioncomprising an oleic alkanolamide and an alkoxylated oleic.

A fuel additive composition as hereinbefore described is especiallycharacterised in that alcohols, and especially ethoxylated alcohols, aresubstantially absent from the composition. Therefore we provide fueladditive as hereinbefore described which is substantially free ofalcohol, especially ethoxylated alcohol.

The oleic alkanolamide is preferably an ethanolamide and more preferablya diethanolamide. Especially preferred are the diethanolamides andparticularly the super diethanolamides.

Generally, there are three commercial routes to alkanolamides;

-   -   Acid+alkanolamine=alkanolamide+water    -   Plant or animal oil        (triglyceride)+alkanolamine=alkanolamide+glycerol    -   Methyl ester+alkanolamine=alkanolamide+methanol

These are listed in order of increasing product quality. The route viathe acid often uses an excess of alkanolamine to produce a producthigher in amide than is obtainable from the acid if a stoichiometricratio is used; these products are sometimes referred to as super amides.

The oleic acid ethoxylate may be derived form a variety of feedstocks,readily available worldwide. However, in a preferred embodiment of theinvention the oleic acid ethoxylate may be produced by ethoxylation oresterification of acids derived from animal fats e.g. beef tallow orvegetable oils, such as soya, etc. Thus the oleic acid precursor may bepredominantly, e.g. from 65–70% v/v, oleic acid, but may also containlinoleic acid, e.g., 10–12% v/v, and may also include small amounts ofstearic, palmitic and/or myristic acids.

The alkoxylate may be an ethoxylate or a propyloxylate or a mixturethereof. The degree of ethoxylation is chosen to optimise performance inthe blend with the oleic diethanolamide and may be from 0.5 to 20, butmore preferably from 0.5 to 10, more preferably from 1 to 3. A suitableproduct within this range would be, for example, that derived from theaddition of 1 molecule of ethylene oxide to 1 mole of oleic acid.

The ratio of the oleic acid alkoxylate to the oleic alkanolamide mayvary, but may be from 99:1 to 1:99 v/v, preferably 3:1 to 1:1 v/v andmost preferably 1:1 v/v.

The additive of the invention may be added to any known hydrocarbonfuel, e.g. diesel, petrol or alcohol, such as ethanol, which may or maynot contain water. The invention is seen to particularly good effectwhen added to fuels based on low fraction oils.

Thus according to a further feature of the invention we provide a fuelcomposition comprising a hydrocarbon fuel and a fuel additive ashereinbefore described.

The concentration of the additive in the fuel composition may varydepending, inter alia, upon the nature of the fuel, however, theconcentration can be very low, typically of the order of from 0.5:1000to 50:1000 v/v, preferably from 1:1000 to 50:1000 v/v, preferably 1:100to 5:100 v/v.

The hydrocarbon fuel may comprise any known hydrocarbon fuel or mixturesthereof, therefore such fuels include but shall not be limited todiesel, e.g., petroleum diesel or biodiesel, gasoline, aviation fuel,alcohol, etc.

In one embodiment of the fuel composition of the invention thehydrocarbon fuel is a petroleum diesel fuel. Such fuels may generally beobtained from the distillation of petroleum and its efficiency can bemeasured by the cetane number. Suitable diesel fuels for use inaccordance with the invention generally have a cetane number of from 35to 60, preferably from 40 to 50. The amount of diesel fuel blended toform the fuel composition of the invention may be from 60% v/v to 95%v/v, based on the total volume of the fuel consumption. The diesel maycomprise petroleum diesel, biodiesel or biodiesel blended with petroleumdiesel in any ratio of from 99:1 to 1:99 v/v.

Preferably, when the fuel of the invention is blend of biodiesel and apetroleum diesel it may comprise up to 50% v/v biodiesel, for examplefrom 1 to 50% v/v, preferably from 5 to 30% v/v, more preferably from 10to 20% v/v.

In a further feature of the invention the hydrocarbon fuel, such adiesel or gasoline may include an amount of an oxygenator, e.g. alcohol,an alkanol, such as ethanol. When an alcohol is present the amount ofalcohol may vary depending, inter alia, upon the nature of the fuel, butmay in an amount of from 1 to 50% v/v, preferably 5 to 20% v/v.

For fuels, ethanol may be produced from fossil fuel feedstocks or byfermentation of sugars derived from grains or other biomass materials.Therefore, ethanol suitable for use in accordance with the fuelcompositions of the invention may be fuel grade ethanol derived fromyeast or bacterial fermentation of starch-based sugars. Suchstarch-based sugars may be extracted from corn, sugarcane, tapioca andsugar beet. Alternatively, fuel grade ethanol may be produced via knowndilute and/or concentrated acid and/or enzymatic hydrolysis of aparticular biomass material for example, from waste industrial sourcesincluding, cellulosic portions of municipal solid waste, waste paper,paper sludge, saw dust. Biomass may also be collected from agriculturalresidues including, for example, rice husks and paper-mill sludge.

A suitable fuel grade ethanol for use in accordance with the inventionmay contain none or only contaminant levels of water. Alternatively, asuitable fuel grade ethanol for use in accordance with the invention maycontain higher amounts of water, up to 5% w/w (hydrous ethanol).

Use of ethanol in combination with a diesel fuel has previously posedproblems wherein the ethanol/diesel fuel mixture would undesirablyseparate into two distinct phases, especially when water is present, andrender the resultant mixture unsuitable for use as a combustible fuel.The use of the fuel additives of the invention permits hydrous ethanolto be blended satisfactorily with conventional diesel fuel withoutforming two phases. The use of fuel grade ethanol blended in accordancewith the invention imparts desirable combustion characteristics to theoverall fuel composition; such as improved fuel stability, lower smokeand particulate matter, lower CO and NOx emissions, improved antiknockcharacteristics, and/or improved anti-freeze characteristics.

When the fuel compositions of the invention are described, the absenceof alcohol from the fuel additive compositions should not be construedas meaning that alcohol, e.g. ethanol, is absent from the fuelcomposition.

The presence of the additive of the invention ensures that the fuelcomposition forms a consistent stable homogenous composition and createsa monolayer simultaneously a result of which leads to a better morecomplete burn which reduces pollution and increases miles per gallon.

As a result a blended fuel, particularly alcohol based, is able tocombust more precisely with a cooler charge to reduce the iron-formatespresent from the aldehyde peracids and peroxide reactions normallyattributable to engine degradation.

In a further aspect of the invention we provide a fuel compositioncomprising a liquid hydrocarbon fuel and a surfactant composition ashereinbefore described.

In the fuel composition of the invention the hydrocarbon fuel, may beany conventionally known fuel, e.g. gasoline, diesel, biodiesel, etc.Furthermore the fuel of the invention may, optionally, include anoxygenator. The oxygenator may be an alcohol, such as ethanol. When anoxygenator such as ethanol is present, the amount of ethanol in the fuelmay vary and may be from 0 to 25% v/v ethanol, preferably from 1 to 10%v/v ethanol.

We further provide a method of running an internal combustion enginecomprising the use of a fuel composition of the invention.

International Patent Application No. WO99/35215, Wenzel, describes anadditive for combustible fuels which includes a nitrogen source, such asurea Whilst the additive is said to reduce NOx, the compositions arevery complex and include numerous ingredients, including:

-   -   a water soluble alcohol,    -   a C6 to C12 alcohol,    -   a C6 to C18 ethoxylated alcohol,    -   a C10 to C24 fatty acid, and    -   a nitrogen source.

We have now surprisingly found that the aforementioned additives aresuitable for use in very low fuel:additive ratios in combination withnitrogenous compounds such as urea.

Thus according to the invention we provide a fuel additive compositioncomprising an oleic alkanolamide, an alkoxylated oleic acid ashereinbefore described and a nitrogen compound.

The nitrogen compound may be selected from the group consisting ofammonia, hydrazine, alkyl hydrazine, dialkyl hydrazine, urea,ethanolamine, monoalkyl ethanolamine, and dialkyl ethanolamine whereinalkyl is independently selected from methyl, ethyl, n-propyl orisopropyl. Urea is preferred. The nitrogen compound may be an anhydrouscompound or a hydrous compound, e.g. an aqueous solution, and may be upto a 5% w/w aqueous solution.

According to a yet further feature of the invention we provide a methodof solubilising a nitrogen compound in a fuel composition whichcomprises mixing a hydrocarbon fuel, a nitrogen compound and a fueladditive as hereinbefore described. The method of the invention mayoptionally include the addition of an alcohol, such as ethanol or water,as hereinbefore described.

We also provide the use of a nitrogen compound in the manufacture of afuel additive of the invention. We especially provide the use of urea inthe manufacture of a fuel additive of the invention.

We further provide a fuel composition comprising a hydrocarbon fuel, afuel additive as hereinbefore described and a nitrogen compound.

In the fuel composition in this aspect of the invention the nitrogencompound may be added by being incorporated into the fuel additive ormay be added separately. Furthermore, the nitrogen compound may be addedas an aqueous solution.

A particular advantage of the present invention over the prior art isthat fuel compositions may be prepared which are substantiallyanhydrous, save for trace water contamination. By the term trace watercontamination we generally mean 0.1% w/w water or less.

Thus, according to a yet further feature of the invention we provide theuse of urea in the manufacture of a fuel composition as hereinbeforedescribed.

The fuel additive or the fuel composition of the invention may alsooptionally comprise a cetane booster in amount of from 0.1% v/v to 10%v/v, based on the volume of the mixture. When a cetane booster isincluded in the fuel composition of the invention it may be added aspart of the fuel additive of the invention or it may be addedseparately.

A suitable cetane booster for use in the mixture is selected from thegroup comprising, 2-ethylhexyl nitrate, tertiary butyl peroxide,diethylene glycol methyl ether, cyclohexanol, and mixtures thereof. Theamount of cetane booster present in the mixture is a function of thecetane value of the particular diesel fuel and the amount of ethanolpresent in the particular fuel composition. Generally, the lower thediesel fuel cetane value, the higher the amount of the cetane booster.Similarly, because ethanol typically acts as a cetane depressant, thehigher the concentration of ethanol in the solution, the more cetanebooster may be necessary in the mixture.

The fuel additives of the invention are advantageous in that, interalia, they are more efficient at producing micro emulsions than priorart additives. Therefore, they are capable of more efficiently producinga stable, clear and homogeneous solution with a hydrocarbon fuel, e.g.diesel/ethanol, even in the presence of water. Therefore, according to afurther feature of the invention we provide a fuel composition ashereinbefore described, which optionally includes an amount of water,and wherein the fuel consists of a substantially stable, substantiallyclear and substantially homogeneous solution.

Furthermore, the fuel additive or the fuel composition of the inventionmay also optionally include a demulsifier in an amount of less than 5%v/v and preferably less than 1% v/v based on the volume of the mixture.

A measure of when a fuel composition is at or near its cloud point isthe conductivity of the fuel. For example, water has a conductivity of100 mS cm⁻¹ and an alcohol, e.g. ethanol, a conductivity of 20 to 30 mScm⁻¹. Fuels, such as gasoline or diesel, being non-polar, have aconductivity of substantially zero. Furthermore, we have found that anon-homogenous mixture of a fuel, such as gasoline or diesel, optionallyincluding an alcohol, such as ethanol, as hereinbefore described, willhave a relatively high conductivity reading, and as homogeneity isapproached, the conductivity will reduce and will reach a minimum whenthe composition is a clear homogenous solution.

Thus according to a further feature of the invention we provide a methodof determining the homogeneity of a fuel composition which comprisesmeasuring the conductivity of the composition.

The conductivity may be measured at varying temperatures. However, wehave found that measuring at substantially ambient temperature ispreferred and particularly at 25.1° C. Conductivity values givenhereinafter generally relate to such values when measured at 25.1° C.Furthermore, since it is known that conductivity may vary withtemperature, any conductivity values taken at differing temperaturesshould be calibrated as if measured at 25.1° C.

We especially provide a method of determining the homogeneity of a fuelcomposition which comprises a fuel and an oxygenator.

The preferred additive of this invention is a non-ionic surfactant andpreferably a blend of surfactants. It is a preferred feature of thisinvention that the surfactants be selected by their nature andconcentration that, in use, the additive (as well as any water or othernon-fuel liquid present) be solubilised within the fuel. For thispurpose it is convenient to have regard to the hydrophilic-lipophilic(HLB) of the surfactant, the value being calculated according to theexpression.

${HLB} = \frac{{{mol}.\mspace{14mu}{wt}}\mspace{14mu}{of}\mspace{14mu}{hydrophilic}\mspace{14mu}{chain} \times 20}{{total}\mspace{14mu}{{mol}.\mspace{14mu}{wt}.}}$

The values will depend on the length of the hydrophilic chain, typicallyan ethoxylate chain. The length of the chain will increase the extent ofsolubilisation because of a greater ability to solubilise.

The invention has the ability to unify the HLB requirements of anyliquid fuel which in turn allows for one dose to be used in any fuelfrom C5 carbon chains up. The benefit being the amount of treatmentdirectly related to the co-solvency ability.

The invention will now be illustrated, but in no way limited, withreference to the accompanying examples.

EXAMPLE 1

Preparation of Compositions

An additive composition was made up by blending constituents, the superdiethanolamide of oleic acid ethoxylated oleic acid in the ration 1:1.1% of this composition was added to 7.7% ethanol/92.3% diesel blends,including certification diesel, US No 1 diesel, 10% aromatic dieselcontaining 0.1% cetane improver resulting in optically clear and stablemicro-emulsion fuels. These were tested as automotive fuels on a 1991Detroit Diesel Series 60 engine using the EPA (USA

Environmental Protection Agency) heavy duty engine certification test asdescribed in the Code of Federal Regulations, Title 40, Part 86, SubpartN.

Toxic exhaust gas omissions were measured and compared with those of thebase un-additised diesels. Significant reductions were obtained of toxicgases CO, CO₂, NOx and particulate matter and the results are shown inTables I–III.

EXAMPLE 2

Test Protocol

Blends were made up of diesel, anhydrous ethanol and water added inconcentrations up to 5% v/v. The cloudy blends were then titratedagainst the additive until clear, stable, micro-emulsions were formed.The volume of additive required to micro-emulsify thediesel/ethanol/water blend was plotted against water content and isshown in FIG. 1. The relative efficiency of additives can be comparedusing this test protocol.

FIG. 1 shows a comparison of the performance of an additive comprisingoleic diethanolamide and an ethoxylated oleic acid in a 1:1 ratiocompared with an additive of the prior art comprising a fatty acidethoxylate a diethanolamide and an ethoxylated alcohol in a ratio of1:1:2.

EXAMPLE 3

Petroleum Diesel/Biodiesel/Ethanol Blend

A blend was made of certification diesel, biodiesel and ethanol,stabilised with the surfactant additive described in Example 1. Emissiontests showed reductions in CO, NOx and particulate matter compared withbase diesel.

EXAMPLE 4

Petroleum Diesel/Ethanol/Urea Blend

Example A solution of 0.25% urea in ethanol was blended in a 7.7:92.3ratio with US No 1 diesel and 1.0% of the additive described in Example1, was added to produce a clear micro-emulsion automotive fuel. Testsusing this blend showed that toxic gas emissions were again lower thanthe base fuel, the urea having made a contribution to the reductionsobtained.

EXAMPLE 5

Gasoline/ethanol Blends

Blends were made up of EPA and CARB gasolines with various amounts ofethanol e.g. a typical blend contained 90% v/v gasoline and 10% ethanol.Small amounts, typically 1% v/v of the additive of the invention wereadded to the gasoline/ethanol blends and the resulting fuels tested asautomotive fuels and the exhaust emissions compared with those of thebase gasolines. The results confirmed that ethanol/gasoline blendscombust to give lower levels of toxic gas emissions.

TABLE I No. 1 Diesel Comparisons THC NOx CO CO₂ PM FUEL Map BHP-hrg/BHP-hr g/BHP-hr g/BHP-hr g/BHP-hr g/BHP-hr Cert Fuel 21.256 0.0904.512 3.849 562.56 0.196 Philips No. 1 Deviance 0.000 0.000 0.000 0.0000.000 0.000 Philips No 2 (for 21.733 0.057 4.648 5.013 567.61 0.262comparison) Deviance from Cert 2.24% −36.67% 3.01% 30.24% 0.90% 33.67%Cert + 7.7% AAE 20.940 0.163 4.425 3.092 558.74 0.142 blend + 2000 EHNDeviance from Cert −1.49% 81.11% −1.93% −19.67% −0.68% −27.55%

TABLE II 10% Aromatic Diesel (CARB Equivalent) Comparisons THC NOx COCO₂ PM FUEL Map BHP-hr g/BHP-hr g/BHP-hr g/BHP-hr g/BHP-hr g/BHP-hr CertFuel 21.733 0.057 4.648 5.013 567.61 0.262 Philips No. 2 Deviance 0.0000.000 0.000 0.000 0.000 0.000 Cert + 7.7% AAE 21.538 0.094 4.668 3.777565.00 0.174 blend + 1000 EHN Deviance from Cert −0.90% 64.91% 0.43%−24.66% −0.46% −33.59% Cert + 8.7% AAE 21.350 0.098 4.630 3.789 565.670.161 blend + 11.3% Bio + 1000 EHN Deviance from Cert −1.76% −71.93%−0.39% −24.42% −0.34% −38.55%

TABLE III 10% Aromatic Diesel (CARB Equivalent) Comparisons THC NOx COCO₂ PM FUEL Map BHP-hr g/BHP-hr g/BHP-hr g/BHP-hr g/BHP-hr g/BHP-hr CertFuel 21.757 0.050 4.318 4.714 554.78 0.249 Philips 10% Aromatic Deviance0.000 0.000 0.000 0.000 0.000 0.000 Cert plus AAE05 only 21.735 0.0414.332 4.885 556.88 0.245 Deviance from Cert −0.10% −18.00% 0.32% 3.63%0.38% −1.61% Cert + 7.7% AAE 21.402 0.122 4.365 3.527 556.14 0.150blend + 1000 EHN Deviance from Cert −1.63 144.00% 1.09% −25.18% 0.25%−39.76% Cert + 7.7% AAE 21.272 0.116 4.344 3.670 559.34 0.161 blend +2000DTBP Deviance from Cert −2.23% 132.00% 0.60% −22.15% 0.82% −35.34%

1. A fuel composition comprising a diesel fuel and a fuel additive,wherein the fuel additive comprises an oleic alkanolamide and analkoxylated oleic acid wherein the additive is substantially free ofethoxylated alcohol.
 2. A fuel composition according to claim 1 whereinthe oleic alkanolamide is an ethanolamide.
 3. A fuel compositionaccording to claim 2 wherein the oleic ethanolamide is a diethanolamide.4. A fuel composition according to claim 1 wherein the alkoxylated oleicacid is an ethoxylated oleic acid, propyloxylated oleic acid or amixture thereof.
 5. A fuel composition according to claim 4 wherein thealkoxylated oleic acid is an ethoxylated oleic acid.
 6. A fuelcomposition according to claim 4 wherein the degree of alkoxylation isfrom 0.5 to 10 mol of alkoxylate to 1 mol of oleic acid.
 7. A fuelcomposition according to claim 6 wherein the degree of alkoxylation is 1mol of alkoxylate to 1 mol of oleic acid.
 8. A fuel compositionaccording to claim 1 wherein the oleic alkanolamide comprises adiethanolamide and the alkoxylated oleic acid comprises an ethoxylatedoleic acid and wherein the ratio of oleic diethanolamide to ethoxylatedoleic acid is from 99:1 to 1:99 v/v.
 9. A fuel composition according toclaim 8 the ratio of oleic diethanolamide to ethoxylated oleic acid is1:1.
 10. A fuel composition according to claim 1 wherein the compositionincludes an amount of water.
 11. A fuel composition according to claim 1wherein the additive to fuel ratio is from 0.5–50:1000 v/v.
 12. A fuelcomposition according to claim 11 wherein the additive to fuel ratio isfrom 1:1000 to 50:1000 v/v.
 13. A fuel composition according to claim 12wherein the additive to fuel ratio is from 1 to 5:1000 v/v.
 14. A fuelcomposition according to claim 1 wherein the diesel fuel is a petroleumdiesel.
 15. A fuel composition according to claim 14 wherein the dieselfuel is a blend of petroleum diesel and biodiesel.
 16. A fuelcomposition according to claim 14 wherein the diesel fuel is abiodiesel.
 17. A fuel composition according to claim 14 wherein the fuelis a mixture of diesel and an alcohol.
 18. A fuel composition accordingto claim 17 wherein the alcohol is ethanol.
 19. A fuel compositionaccording to claim 17 wherein the fuel is a hydrous ethanol/dieselblend.
 20. A fuel composition according to claim 19 wherein the additiveto fuel ratio is up to 5% v/v.
 21. A fuel composition according to claim17 wherein the fuel is an anhydrous ethanol/diesel blend.
 22. A fuelcomposition according to claim 1 further including a nitrogen compound.23. A fuel composition according to claim 22 wherein the nitrogencompound is selected from the group consisting of the ammonia,hydrazine, alkyl hydrazine, dialkyl hydrazine, urea, ethanolamine,monoalkyl ethanolamine, and dialkyl ethanolamine, wherein the alkyl isindependently selected from methyl, ethyl, n-propyl or isopropyl.
 24. Afuel composition according to claim 23 wherein the nitrogen compound isurea.
 25. A method of manufacturing a fuel composition according toclaim 1 comprising the steps of: providing a DIESEL fuel, adding thefuel additive of claim 1 and adding a nitrogen compound.
 26. The methodaccording to claim 25 wherein the nitrogen compound is urea.
 27. A fuelcomposition according to claim 1 wherein the fuel composition alsocomprises a cetane booster in amount of from 0.1% v/v to 10% v/v.
 28. Afuel composition according to claim 1 wherein the additive alsocomprises a demulsifier in an amount of less than 5% v/v.